HEPARIN AMELIORATES PULMONARY-HYPERTENSION INDUCED BY PLATELET-ACTIVATING-FACTOR IN PIGS

The purpose of this study was to investigate the effects of heparin on the haemodynamic changes which were induced by platelet-activating fa ctor in the pulmonary and systemic circulation in pigs. Mean arterial pressure and mean pulmonary arterial pressure were measured continuous ly in five anaesthetised juvenile pigs, Bolus doses of platelet-activa ting factor (0.2-2 mu g) were given intravenously to establish a dose response curve. Heparin (300 units/kg) was given intravenously. Thirty minutes later, the same doses of platelet-activating factor were repe ated to establish a second dose response curve. Platelet-activating fa ctor caused a dose dependent pulmonary artery hypertension, associated with an initial systemic hypotension followed by systemic hypertensio n. Heparin effectively reduced the low dose (0.2 mu g) platelet-activa ting factor-induced pulmonary arterial hypertension (p<0.01) but not t he higher doses. It had no effect on the platelet-activating factor-in duced systemic hypotension or hypertension. The pulmonary and systemic circulation responded differently to platelet-activating factor after giving heparin, While heparin ameliorated the platelet-activating fac tor-induced pulmonary hypertension, it did not affect the changes in t he systemic circulation. (C) 1998 Elsevier Science Ltd.